Lycopene's Role In Reducing The Risk Of Prostate Cancer

Who would have thought that one of a man?s best sources of protection against prostate cancer is a tomato? The substance that gives the tomato its deep red color may also reduce a man?s risk of developing prostate cancer by 35%.

The tomato?s newfound miracle nutrient is called lycopene, and it belongs to a family of natural pigments (carotenoids) found in plants and animals. Beta carotene, the orange-colored precursor to vitamin A, is probably the best known of the approximately 500 carotenoids found in nature.

According to the most current research, lycopene is a top-flight antioxidant, obtained through the diet from tomatoes (or, now, from lycopene supplements) and capable of protecting the body against many degenerative diseases, including cancer.

Researchers from Harvard University Medical School studied 47,894 men, age 40 to 75 and free of any diagnosed cancer, over a six-year period. Their dietary preferences and consumption frequency for 131 foods and beverages were assessed, providing researchers a detailed picture of the yearly nutrient intake of each man.

Of the 46 foods, tomato sauce, tomatoes, pizza, and strawberries were associated with a reduced risk of prostate cancer. The researchers learned that the first three of these foods were the primary dietary sources of lycopene, accounting for 82% of the lycopene intake for the men. (While strawberries were associated with a reduced prostate cancer risk, they are not a significant source of lycopene.) Those who consumed ten or more servings of these three tomato-based foods per week had a 35% reduced chance of developing prostate cancer.

The lycopene in these foods is one of five groups of carotenoids: No measurable protective effect against prostate cancer was noted among the four other primary carotenoids: alpha carotene (found in carrots), beta carotene (in yams, sweet potatoes, yellow squash), lutein (found in dark green, leafy vegetables), and beta-cryptoxanthin (in oranges).

It?s important to know that lycopene is the predominant carotenoid found in the blood, in various tissues (such as liver, kidney, adrenal glands, testes, and ovaries), and in the prostate gland itself. Research suggests that lycopene is an essential part of the body?s natural defense against harmful oxidizing agents such as free radicals. Lycopene is now being touted as a highly capable antioxidant; Dr. Giovannucci pointed out that copene is the most efficient scavenger of singlet oxygen [free radicals] among the common carotenoids.?

If tomatoes are a key factor in natural prostate protection, it?s logical that food scientists would seek a lycopene-rich strain. Scientists in Israel, working for Lyco-Red Natural Products Industries in Beer-Sheva, used traditional cross-breeding methods to produce a tomato with up to four times more lycopene than is found in regular tomatoes.

The extract from these hybridized tomatoes (grown by organic methods) is called Lyc-O-Mato? and it takes two metric tons of the lycopene-enriched tomatoes to produce one gram of the lycopene extract, which is mixed with tomato oil, beta carotene, and vitamin E for better absorption and additional antioxidant benefits. The Lyc-O-Mato? extract is now used in at least 13 nutritional supplements.

A diet rich in carotenoid-containing foods is associated with a number of health benefits. Lycopene provides the familiar red color to tomato products and is one of the major carotenoids in the diet of North Americans and Europeans. Interest in lycopene is growing rapidly following the recent publication of epidemiologic studies implicating lycopene in the prevention of cardiovascular disease and cancers of the prostate or gastrointestinal tract. Lycopene has unique structural and chemical features that may contribute to specific biological properties. Data concerning lycopene bioavailability, tissue distribution, metabolism, excretion, and biological actions in experimental animals and humans are beginning to accumulate although much additional research is necessary.

Increasing clinical evidence supports the role of lycopene as a micronutrient with important health benefits, because it appears to provide protection against a broad range of epithelial cancers. Tomatoes and related tomato products are the major source of lycopene compounds, and are also considered an important source of carotenoids in the human diet. Undesirable degradation of lycopene not only affects the sensory quality of the final products, but also the health benefit of tomato-based foods for the human body. Lycopene in fresh tomato fruits occurs essentially in the all-trans configuration. The main causes of tomato lycopene degradation during processing are isomerization and oxidation. Isomerization converts all-trans isomers to cis-isomers due to additional energy input and results in an unstable, energy-rich station. Determination of the degree of lycopene isomerization during processing would provide a measure of the potential health benefits of tomato-based foods. Frozen foods and heat-sterilized foods exhibit excellent lycopene stability throughout their normal temperature storage shelf life. Lycopene bioavailability (absorption) can be influenced by many factors. The bioavailability of cis-isomers in food is higher than that of all-trans isomers. Lycopene bioavailability in processed tomato products is higher than in unprocessed fresh tomatoes. The composition and structure of the food also have an impact on the bioavailability of lycopene and may affect the release of lycopene from the tomato tissue matrix. Food processing may improve lycopene bioavailability by breaking down cell walls, which weakens the bonding forces between lycopene and tissue matrix, thus making lycopene more accessible and enhancing the cis-isomerization.

More information on lycopene bioavailability, however, is needed. The pharmacokinetic properties of lycopene remain particularly poorly understood. Further research on the bioavalability, pharmacology, biochemistry, and physiology must be done to reveal the mechanism of lycopene in human diet, and the in vivo metabolism of lycopene. Consumer demand for healthy food products provides an opportunity to develop lycopene-rich food as new functional foods, as well as food-grade and pharmaceutical-grade lycopene as new nutraceutical products. An industrial scale, environmentally friendly lycopene extraction and purification procedure with minimal loss of bioactivities is highly desirable for the foods, feed, cosmetic, and pharmaceutical industries. High-quality lycopene products that meet food safety regulations will offer potential benefits to the food industry.

Lycopene has been identified as a phytochemical with potentially protective health benefits. The cellular content of lycopene and other tomato-related carotenoids with proposed beneficial health effects can be increased through prolonged supplementation.

Lycopene, the main carotenoid in tomato, has been shown to be a potent antioxidant in vitro. However, there is no significant evidence of its antioxidant action in vivo. We evaluated the effect of tomato intake on plasma carotenoid concentrations and lymphocyte resistance to oxidative stress... Tomato consumption also had an effect on cellular antioxidant capacity: lymphocyte DNA damage after ex vivo treatment with hydrogen peroxide decreased by 42% in the groups of subjects after consumption of the tomato diet. CONCLUSION: The consumption of tomato products may reduce the susceptibility of lymphocyte DNA to oxidative damage.

Dietary consumption of the carotenoid lycopene (mostly from tomato products) has been associated with a lower risk of prostate cancer. Evidence relating other carotenoids, tocopherols, and retinol to prostate cancer risk has been equivocal. This prospective study was designed to examine the relationship between plasma concentrations of several major antioxidants and risk of prostate cancer... In the placebo group, plasma lycopene was very strongly related to lower prostate cancer risk (5th quintile OR = 0.40; P, trend = 0.006 for aggressive cancer), whereas there was no evidence for a trend among those assigned to beta-carotene supplements. However, in the beta-carotene group, prostate cancer risk was reduced in each lycopene quintile relative to men with low lycopene and placebo. The only other notable association was a reduced risk of aggressive cancer with higher alpha-tocopherol levels that was not statistically significant. None of the associations for lycopene were confounded by age, smoking, body mass index, exercise, alcohol, multivitamin use, or plasma total cholesterol level. These results concur with a recent prospective dietary analysis, which identified lycopene as the carotenoid with the clearest inverse relation to the development of prostate cancer. The inverse association was particularly apparent for aggressive cancer and for men not consuming beta-carotene supplements. For men with low lycopene, beta-carotene supplements were associated with risk reductions comparable to those observed with high lycopene. These data provide further evidence that increased consumption of tomato products and other lycopene-containing foods might reduce the occurrence or progression of prostate cancer.

The epidemiologic literature in the English language regarding intake of tomatoes and tomato-based products and blood lycopene (a compound derived predominantly from tomatoes) level in relation to the risk of various cancers was reviewed. Among 72 studies identified, 57 reported inverse associations between tomato intake or blood lycopene level and the risk of cancer at a defined anatomic site; 35 of these inverse associations were statistically significant. No study indicated that higher tomato consumption or blood lycopene level statistically significantly increased the risk of cancer at any of the investigated sites. About half of the relative risks for comparisons of high with low intakes or levels for tomatoes or lycopene were approximately 0.6 or lower. The evidence for a benefit was strongest for cancers of the prostate, lung, and stomach. Data were also suggestive of a benefit for cancers of the pancreas, colon and rectum, esophagus, oral cavity, breast, and cervix. Because the data are from observational studies, a cause-effect relationship cannot be established definitively. However, the consistency of the results across numerous studies in diverse populations, for case-control and prospective studies, and for dietary-based and blood-based investigations argues against bias or confounding as the explanation for these findings. Lycopene may account for or contribute to these benefits, but this possibility is not yet proven and requires further study. Numerous other potentially beneficial compounds are present in tomatoes, and, conceivably, complex interactions among multiple components may contribute to the anticancer properties of tomatoes. The consistently lower risk of cancer for a variety of anatomic sites that is associated with higher consumption of tomatoes and tomato-based products adds further support for current dietary recommendations to increase fruit and vegetable consumption.

Known hazards: People with arthritis who are allergic to tomatoes and other members of the nightshade family should consult their physician first before taking lycopene.

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